A study of the physicochemical and surface properties of tooth apatites is proposed to develop a better understanding of basic phenomena that may control the behavior of teeth in their natural environments. A number of investigations will be carried out to study various interfacial phenomena that may influence the response of tooth apatites to a wide variety of conditions. Through such investigations we should be able to obtain the kinds of detailed information about apatite surface chemistry that should help find ways to prevent dental caries and assist in finding suitable restorative adhesive materials. Simultaneous measurements of calcium, phosphate and hydrogen ions will be made to establish the dissolution characteristics of hydroxyapatites. These studies will be coupled with electrokinetic measurements to establish the relationship between dissolution, surface composition, and electrokinetic phenomena. Factors that affect the uptake of fluoride ions wll be correlated with the dissolution and electrical double layer properties. The mechanism of adsorption of various trace metals and organic surface active agents will be determined and correlated with the interfacial behavior of tooth apatites. Pore size distributions of dental materials will be determined to ascertain how they may influence interfacial behavior. The stability of thin aqueous films as measured by suitable optical techniques will be correlated with the wetting behavior of tooth apatites. Gravimetric adsorption techniques will be used to study the influence of representative gaseous components of tobacco smoke on the interfacial properties of tooth apatite.